An antecedent potential (AP) and a positive spike potential (SP) that precede voluntary saccadic eye movements have been described in normal human subjects using averaged evoked potential techniques. These responses can be recorded over parietal cortex (P3P4) with linked ear reference. Preliminary studies suggest that this potential is related to synthesis of visual information arriving in the posterior parietal lobe via extra-geniculostriate pathways which involve the ipsilateral superior colliculus and pulvinar. It is hypothesized that this potential is produced by a pool of neurons, similar to that described in subhuman primates, which is involved in selective visual attention and reorientation. The purpose of the proposed study is: (1) to establish normative data for the latency, amplitude, and directional characteristics of this potential in various age groups, and (2) to investigate the relation of these potentials to various stimulus parameters for saccadic eye movements. These parameters include (a) the presence or absence of visual input, (b) saccade direction, (c) saccade amplitude, and (d) the attentional/motivational status of the subject. It is anticipated that the proposed study will require two years for completion. Although the present proposal is limited to the acquisition of normative data and the relationship of the potential to various stimulus parameters, it is anticipated that future proposals will: (1) investigate the neural structures involved in the generation of this potential by studying patients with lesions at various sites in the nervous system, and (2) determine the sensitivity and specificity of this test in the diagnosis of various neurologic disorders including multiple sclerosis, progressive supranuclear palsy, and others.